Research Of TMDC-FET Based On Laser Direct Writing

With the development of internet,internet of things and mobile intelligent terminals,the core part of integrated circuits?IC?has also made rapid progress.From the first practical integrated circuit in 1960 to today's ultra large scale integrated circuit?VLSI?,the transistor's characteristic size has reached 14 nm.However,as the transistor scale decreases,the difficulty of the process increases.With the in-depth study of two dimensional materials,it is theoretically feasible to reduce transistor characteristic size to 1 nm scale by the transistor formed by its interlayer,because it has only one atom or molecular layer.In this thesis,we use the two-dimensional material WS₂?2D-TMDC?to make the electrodes on WS₂ single crystal by laser direct writing and study the transistor performance of WS₂.The main contents are as follows:?1?A laser direct writing system is set up in this paper,in order to solve the problem of making the electrode graphics,in the process of making WS2 transistors.This thesis mainly includes two parts to build the laser direct writing system,the first part is the hardware of the laser direct writing system.It includes design of light path,the electric displacement platform,optical switch and other related hardware,as well as the choice of the optical system and related hardware installation and debugging.The second part is the design of laser direct writing software program.This part mainly imports the graphics which are designed in CAD to the program.The program is transformed into the switch of light and platform motion based on the design graph,and then finished the designed figure on the photoresist.?2?After the construction of the laser direct writing system,the study of photolithography metal stripping process was carried out.This thesis mainly studies the factors that affect the quality of the lithography line,including the influence of laser power stability,and the influence of two scanning methods designed in this thesis on the quality of the lithography line.The finest line width of the laser direct writing system is about 1?m,after optimizing the photolithography parameters,and we studied the laser direct writing metal lift off process.Finally,we selected the double-layer photoresist metal lift off process.?3?We studied the growth of WS₂,for the final fabrication of two-dimensional material WS₂ based transistors.Through the comparison of various growth methods,the method of chemical vapor deposition?CVD?was used to grow WS2 in this paper.The properties of the grown materials were characterized by optical,Raman and AFM.After characterization of the materials,the two-dimensional materials grown on SiO₂/Si substrates were transferred to Al₂O₃/SiO₂/Si substrates for subsequent fabrication of transistor devices on Al₂O₃/SiO₂/Si substrates.?4?We used laser direct writing system to make transistor devices on Al₂O₃/SiO₂/Si substrate,and tested the transistors'performance.According to the test results,we calculated the basic parameters of transistors,and analyzed these parameters.The transistor switch ratio produced in this article is about 10⁵.It has a certain application prospect from the view of switch ratio.